The purpose of this paper is to look from a very general viewpoint to the interaction of factors which contribute to the process of aging. Life time is the most significant period for an individual. Several theories try to explain the process of aging by genetic determinants, by genetic or metabolic defects, by immunologic failure or by other reasons. It is noteworthy that the duration of life is correlated to the size of the body of different animals. This fact indicates a close relation to metabolism. It can be assumed that under optimal conditions of life, defects in function or structure are repaired by special maintenance functions. During the process of aging these functions lose effectuality.